1. Field of the Invention
The present invention relates to a carrier changer, more particularly, to a carrier changer capable of generating a plurality of pseudo carriers by one pseudo carrier generator.
2. Prior Art
FIG. 1 is a block diagram for showing a configuration of a conventional carrier changer. The conventional carrier changer includes a traffic signal generator 102, a directional coupler 104, a divider 106, a plurality of carrier changing sections 108, a synthesizer 110, and a plurality of power amplifiers 112.
The traffic signal generator 102 generates a forward signal. A directional coupler 104 receives the forward signal from the traffic signal generator 102 and outputs it to a plurality of power amplifiers 112. The directional coupler 104 generates a pseudo carrier generating signal based on the traffic signal. The divider 106 divides the pseudo carrier generating signal into a plurality of signals. The plurality of carrier changing sections 108 generate a plurality of pseudo carrier signals F2, F3, F4, . . . , Fn based on the plurality of pseudo carrier generating signals from the divider 106. The synthesizer 110 synthesizes the plurality of pseudo carrier signals F2, F3, F4, . . . , Fn generated by the plurality of carrier changing sections 108. The plurality of power amplifiers 112 amplifies powers of the forward signal and the plurality of pseudo carrier signals F2, F3, F4, , . . . , Fn from the directional coupler 104.
According to the conventional carrier changer, since the number of carrier changing sections corresponding to the number of pseudo carriers to be generated, a divider, and a synthesizer are used, insertion loss is generated. In order to compensate for insertion loss, an additional power amplifier should be used.
U.S. Pat. No. 5,297,136 (issued to Claudio Soprano et al. on Mar. 22, 1994) discloses a multicarrier demodulator to demodulate simultaneously a great number of data channels having low and medium data rates, that is data rates lower than 4 Mbit/s.
Therefore, it is an object of the present invention, for the purpose of solving the above mentioned problems, to provide a carrier changer capable of generating a plurality of pseudo carriers by one pseudo carrier generator.
In order to attain the object, according to the present invention, there is provided a carrier changer comprising:
a pseudo carrier generator for selectively generating one of a plurality of forward pseudo carrier signals based on a forward signal by a time division;
a forward signal processor for receiving the forward signal and generating a pseudo carrier generating signal based on the forward signal, and outputting the forward signal and the pseudo carrier signals generated by the pseudo carrier generator; and
Preferably, the pseudo carrier generator includes a first band pass filter for band pass filtering the pseudo carrier generating signal at a first predetermined bandwidth; a first amplifier for amplifying an output signal of the first band pass filter; an intermediate frequency generator for converting an output signal of the first amplifier into an intermediate frequency signal; an intermediate frequency amplifier for amplifying the intermediate frequency signal from the intermediate frequency generator according to a gain of the pseudo carrier generating signal; a frequency converter for generating one of the forward pseudo carrier signals based on an output signal of the intermediate frequency amplifier according to a variable phase locked loop frequency data; a second amplifier for amplifying the one of the forward pseudo carrier signal from the frequency converter; and a second band pass filter for band pass filtering an output signal of the second amplifier at a second predetermined bandwidth.
More preferably, the forward signal processor includes a first directional coupler for receiving and outputting the forward signal, and generating the pseudo carrier generating signal based on the forward signal by a loose coupling; a circulator for preventing the forward signal from the first directional coupler from outputting in a reverse direction; and a second directional coupler for outputting the forward pseudo carrier signal from the pseudo carrier generator and an output signal of the circulator by a loose coupling.
Also, there is provided a carrier changer comprising:
a pseudo carrier generator for selectively generating one of a plurality of pseudo carrier signals based on a one of a plurality of forward signals by a time division;
a plurality of forward signal processors each for receiving a forward signal, and outputting the forward signal and the pseudo carrier signal generated by the pseudo carrier generator;
a switch section for sequentially switching the forward signal and switching the pseudo carrier signal corresponding to the switched forward signal; and a plurality of power amplifiers each for amplifying powers of the forward signal and the pseudo carrier signals from one of the forward signal processors switched by the switch section.
Since an output of a phase locked loop is generated according to a variable phase locked loop data, pseudo carrier signals having different frequencies can be obtained by one pseudo carrier generator. Since one power amplifier a plurality of pseudo carries signals, additional amplifiers need not being used. Since a plurality of pseudo carrier signals are generated by a time division, insertion loss due to usage of a divider and synthesizer is not generated.